This invention relates to the field of computer based viewing hardware with fluoroscopic tools for cardiac surgery, and more particularly to viewing devices for myocardial revascularization.
Heart disease is a significant health problem which has been the subject of substantial medical study. Bypass surgery has become commonplace; yet such surgery may be unavailable to many patients, either because of the nature of the occlusions or the physical condition of the patient. One promising alternative technique for treating such cases is known as transmyocardial revascularization (TMR). Although this technique was considered as early as the work of Dr. C. Beck xe2x80x9cThe Development of a New Blood Supply to the Heart By Operationxe2x80x9d, Annals of Surgery, Vol. 102, No. 5 (11/35) pp. 801-813, the method was not extensively studied until the work of Dr. M. Mirhoseini and M. Cayton, an example of which is found in xe2x80x9cLasers in Cardiothoracic Surgeryxe2x80x9d in Lasers in General Surgery (Williams and Williams; 1989) pp. 216-223.
Myocardial revascularization systems used by interventional cardiologists include a percutaneous myocardial revascularization (PMR) instrument that is a catheter and tissue removal energy delivery system that creates channels partially into the myocardium from inside the left ventricle. In the PMR procedure, an interventional cardiologist performs a cardiac catheterization procedure using a catheter with an internal optical fiber that is inserted into the femoral artery at the groin and advanced through the heart""s aorta arch into the left ventricle. Once in the ventricle, the catheter is guided to the endocardium where the device creates pathways through the endocardium and partially into the myocardium.
PMR generally requires that a physician use a hand-held device that encompasses and guides either a mechanical cutting device or one or more optical fibers through which laser energy is directed. Mechanical or laser energy cuts or vaporizes heart muscle tissue immediately in front of the distal end of the device. From the standpoint of safety and efficacy, the laser based procedures minimize both ancillary tissue damage and embolic material production, both results are highly desirable. Varying penetration depths are possible. Clinical tests have demonstrated that revascularization channels/pathways, which generally communicate with the ventricle, facilitate revascularization of the heart muscle and recovery of heart function.
U.S. Pat. No. 5,876,373 entitled xe2x80x9cSteerable Catheterxe2x80x9d, issued Mar. 2, 1999, based on application Ser. No. 08/833,352, filed Apr. 4, 1997 by Giba et al., U.S. patent application Ser. No. 09/156,963, entitled xe2x80x9cSteerable Catheter with Tip Alignment and Surface Contact Detectorxe2x80x9d, filed Sep. 18, 1998 by Khairkahan et al., and U.S. patent application Ser. No. 09/326,118, entitled xe2x80x9cNon-deforming, Deflectable Multi-lumen Catheterxe2x80x9d and filed Jun. 4, 1999, are incorporated herein by reference in their entirety. These applications teach steerable catheters and methods of use, particularly adapted for PMR use. The distal portion of the catheters are deflectable. Rotation of the catheters, therefore, such as within the left ventricle during a PMR procedure, will allow treatment of essentially any surface area within the ventricle. The catheters have a relative movement compensation mechanism for maintaining positioning between the distal portion of the catheter and the functional device, such as an energy delivery device disposed therein. The deflectable portion of the catheter is non-deformable.
Another approach to catheter construction for PMR is described in International Publication WO 96/35469, entitled xe2x80x9cSystem for Treating or Diagnosing Heart Tissuexe2x80x9d, International Application No. PCT/US96/06700, filed May 9, 1996, to Kesten et al., and WO 98/39045, entitled xe2x80x9cCatheter with Three Sections of Different Flexibilitiesxe2x80x9d, International Application No. PCT/US98/04484, filed Mar. 6, 1998, to Javier et al., are also hereby incorporated by reference in their entirety. In these systems, an aligning catheter, shaped to extend along the long axis of the left ventricle, guides a laser catheter to various and predetermined individual points within the left ventricle. The intraluminal catheter has an elongated tubular shaft with proximal, intermediate, and distal shaft sections for positioning a therapeutic or diagnostic device within a patient""s body region such as a heart chamber. The intermediate shaft section has greater flexibility than the proximal or distal shaft sections, and is preferably of sufficient flexibility to easily assume the curvature of the patient""s aortic arch, and reduce the force of contact between the catheter distal end and tissue defining the patient""s body region to thereby reduce restriction on the rotation of the catheter. The flexible intermediate shaft section is preferably of a length to occupy a significant portion of the arctic arch, and the catheter overall length is preferably sufficient to have a catheter proximal extremity extending out of the patient and a distal extremity extending at least into an aortic passageway adjacent the patient""s left ventricle. In embodiments, the distal section of a guiding or first delivery catheter, is provided with a double bend, or other predetermined geometry and dimension, to facilitate a perpendicular approach by a laser or other energy delivery device to the surface of the endocardium of the left ventricle.
Fluoroscopy is used in PMR and other intracardiac catheter-based procedures for guidance and visual marking, to locate the optical fiber""s distal end inside the heart for proper channel formation and prevent excessive penetration thereof into the myocardium. A plastic transparency may be placed on the fluoroscope monitor, the shape of the ventricle manually traced using an ink marker, and then manually marking the channels as they are formed. The manual markings are often not drawn on the transparency exactly where the interventional cardiologist, having a slightly different optical vantage point of the procedure, might see the references, thereby increasing the complexity of the positioning the catheter and estimating the precise position inside the left ventricle to form channels. Furthermore, manually drawing an outline of the left ventricle based on a fluoroscopic image, which is moving according to the cardiac or respiratory cycles, can be problematic. Additionally, dye typically injected to enhance the fluoroscopic image has a short duration. Moreover, since most current fluoroscopy imaging systems are two-dimensional based imaging systems, the cardiologist must monitor two perpendicular planar images of a heart to view a PMR""s optical fiber""s position in a three-dimensional perspective by switching between two images. Furthermore, tracking already created channels is a problem since the screen may not readily show locations of these previously created channels. Additionally, excessive radiation while using a fluoroscope system poses radiation hazards to patient and operating room personnel.
U.S. Pat. No. 5,369,678 entitled xe2x80x9cMethod for tracking a catheter probe during a fluoroscopic procedure,xe2x80x9d by Chiu, teaches of fluoroscopy for monitoring the location of a catheter inside a body during balloon angioplasty or laser ablation for percutaneous interventional procedures. Chiu teaches a method for determining catheter tip location from fluoroscopic images using digital imaging processing techniques that confine full X-ray dosage to a central area, compensating for the reduced X-ray dosage in the peripheral areas by computer imaging enhancement but does not solve the problems currently associated with the use of fluoroscopy for guidance and visual marking in PMR and other intracardiac catheter-based procedures.
It is desirable to have apparatus and methods that use integrated hardware of a computer workstation, video capture, image display and manipulation and angular feedback from the fluoroscopy device to assist the cardiologist during the PMR procedure. There is a further need for apparatus and method that solves the problems associated with the use of fluoroscopy for guidance and visual marking in PMR and other intracardiac catheter-based procedures. Furthermore, there is a need to reduce the complexity of positioning such catheters and estimating the precise position inside the left ventricle to form channels during myocardial revascularization.
This invention describes a method of using computer based image processing techniques to automate this process as well as adding new capabilities to allow faster and more accurate placement of channels. An advantage of the disclosed invention is to solve the problem of determining catheter location within the left ventricle.
It is a further advantage to replace the current manual channel mapping technique with a computerized, video-based map. The computer-based channel map would also have greater accuracy than the manual map.
The present invention is a method to use fluroscopic image processing preferably in combination with specifically designed radio opaque markers on the distal portion of an intraventricular catheter to provide accurate information regarding the location and orientation of the catheter. This would be a useful enhancement to the PMR procedure. The distal portion of the intraventricular catheter is marked with asymmetric markers that are spaced a known distance apart on at least two portions of the catheter that are roughly orthogonal to each other, or at least or on two portions of the catheter that have a known angle between them.
The fluoroscopic image is processed using image-processing techniques that use edge-detection and pattern recognition to determine the 2-D location of these markers. The software then compares the 2-D geometry to the known spatial relations of the various markers and derives the true 3-dimensional location and orientation of the catheter. This invention provides additional accurate information regarding catheter position and orientation without requiring any imaging modalities other than fluoroscopy, which is already in use for these procedures. The combination of specifically designed system of markers, which may be radially asymmetric in order to provide information regarding rotational orientation, with edge-detection and pattern-recognition software provides location and orientation information for a catheter used in intraventricular procedures.
It is a further advantage of the present invention to decrease the degree to which the fluoroscopy related PMR procedure is dependent upon orthogonal visualization capability or means, thus allowing the user to remain predominantly in an RAO-30 projection throughout most of the procedure
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.